Feather

Most of the feathers of the last 120 million years are/were of two types. Pennaceous feathers have a rachis (or vane) in the middle, while plumulaceous feathers do not. We know plumulaceous feathers as "down." Both are composed chiefly of barbs, which branch fractally into paired barbules. Pennaceous feathers use the barbules to make a watertight seal and reduce air friction, while in the tangle of hair-stuff that is a plumulaceous feather, trapped air provides insulation.

Pennaceous feathers subdivide two ways: contour and flight. In contour feathers the rachis is centered, contouring the feather to the body (picture the bottom of a boat). The rachis is off-center in flight feathers, which creates aerodynamic effects; these effects and their functions are determined by the relative volumes of barb on either side of the rachis. Examine the feathers from, say, an inner wing versus a wing-tip versus a tail for illustration. From small adjustments bloom large consequences.

Some feathers embody features of both pennaceous and plumulaceous feathers. These are known as "semi-plumes" and occupy the space between contour and downy feathers. Other, less common feathers include bristles and filoplumes, unbarbed sensory organs that register pressure and vibration. And eyelashes.

There are three kinds of feather pigments: melanin, same granules of color that appear in human and animal hair; carotenoids, which are retained through the eating of pigmented plants; and porphyrins, which are derived from amino acids. These shine bright red under ultraviolet light, and appear on owls.

Growth starts with a thickening of both the dermis and epidermis. This assembly of condensed cells is known as a placode. The placode becomes a feather germ after some elongation; the follicle forms by the proliferation of cells in a ring around the germ's base, with the old cells migrating downwards. This shortly creates a deep, ring-shaped depression around the feather germ. The portion of the germ surrounded by the depression is the follicle, which fills with dermal pulp and receives an artery. Continued downward movement of old cells from the follicle's epidermis forces the oldest cells up through the center. This is also how hair grows.

The rachis forms when, on the innermost surface of the follicle, ribs of keratin grow helically, meeting in a spine on one side of the follicle. The feather takes shape as the rachis emerges from the follicle and its ribs of keratin, its barbs lined with barbules, unfurl.

Dinosaur Feathers

The first creatures known to possess flight feathers are carnivorous theropoddinosaurs. 125-million-year-old Microraptor gui fossils unearthed in China are fringed with the shadows of long, pennaceous, asymmetrical feathers; Caudipteryx fossils reveal feathers at the ends of unfused fingers. (Birds have fingers, but they're fused).

The origin of feathers touches the bigger question of evolutionary novelties--structures without antecedents or contemporaries. The current theory is that both kinds of feathers evolved in stages, beginning with a hollow cylinder similar to a pin feather. This evolved into a tuft of smooth barbs; this then evolved into a tuft of rough barbs, or a plumulaceous feather.

Pennaceous feathers began as smooth barbs fused symmetrically to a central rachis; they were not capable of generating lift. Next came barbules, then hooked barbules. Flight feathers appeared last. The creatures they clothed were hellish; Euornithes had a toothed beak as long as its body, and Archaeopteryx had a long, bony, feathered tail.

The aforementioned Microraptor had four wings.

The theory that feathers evolved in independent, novel stages is a recent one. The previous theory, toppled by the Chinese fossils, was that feathers evolved from elongate scales. Also diminished is the line between dinosaurs and birds. The functions of most early feathers is not completely understood; it is suspected they were used for courtship, defense, insulation, and water repellency.

One of the peculiar dermal appendages, of several kinds, belonging to birds, as contour feathers, quills, and down.

An ordinary feather consists of the quill or hollow basal part of the stem; the shaft or rachis, forming the upper, solid part of the stem; the vanes or webs, implanted on the rachis and consisting of a series of slender laminae or barbs, which usually bear barbicels and interlocking hooks by which they are fastened together. See Down, Quill, Plumage.

2.

Kind; nature; species; -- from the proverbial phrase, "Birds of a feather," that is, of the same species.

[R.]

I am not of that feather to shake off
My friend when he must need me.
Shak.

3.

The fringe of long hair on the legs of the setter and some other dogs.

A longitudinal strip projecting as a fin from an object, to strengthen it, or to enter a channel in another object and thereby prevent displacement sidwise but permit motion lengthwise; a spline.

7.

A thin wedge driven between the two semicylindrical parts of a divided plug in a hole bored in a stone, to rend the stone.

Knight.

8.

The angular adjustment of an oar or paddle-wheel float, with reference to a horizontal axis, as it leaves or enters the water.

Feather is used adjectively or in combination, meaning composed of, or resembling, a feather or feathers; as, feather fan, feather-heeled, feather duster.

Feather alumMin., a hydrous sulphate of alumina, resulting from volcanic action, and from the decomposition of iron pyrites; -- called also halotrichite. Ure. -- Feather bed, a bed filled with feathers. -- Feather driver, one who prepares feathers by beating. -- Feather duster, a dusting brush of feathers. -- Feather flower, an artifical flower made of feathers, for ladies' headdresses, and other ornamental purposes. -- Feather grassBot., a kind of grass (Stipa pennata) which has a long feathery awn rising from one of the chaffy scales which inclose the grain. -- Feather maker, one who makes plumes, etc., of feathers, real or artificial. -- Feather oreMin., a sulphide of antimony and lead, sometimes found in capillary forms and like a cobweb, but also massive. It is a variety of Jamesonite. -- Feather shot, or Feathered shot Metal., copper granulated by pouring into cold water. Raymond. -- Feather sprayNaut., the spray thrown up, like pairs of feathers, by the cutwater of a fast-moving vessel. -- Feather star. Zool. See Comatula. -- Feather weight. Racing (a) Scrupulously exact weight, so that a feather would turn the scale, when a jockey is weighed or weighted. (b) The lightest weight that can be put on the back of a horse in racing. Youatt. (c) In wrestling, boxing, etc., a term applied to the lightest of the classes into which contestants are divided; -- in contradistinction to light weight, middle weight, and heavy weight.

A feather in the cap an honour, trophy, or mark of distinction. [Colloq.] -- To be in full feather, to be in full dress or in one's best clothes. [Collog.] -- To be in high feather, to be in high spirits. [Collog.] -- To cut a feather. (a) Naut. To make the water foam in moving; in allusion to the ripple which a ship throws off from her bows. (b) To make one's self conspicuous.[Colloq.] -- To show the white feather, to betray cowardice, -- a white feather in the tail of a cock being considered an indication that he is not of the true game breed.

An eagle had the ill hap to be struck with an arrow feathered from her own wing.
L'Estrange.

2.

To adorn, as with feathers; to fringe.

A few birches and oaks still feathered the narrow ravines.
Sir W. Scott.

3.

To render light as a feather; to give wings to

.[R.]

The Polonian story perhaps may feather some tedions hours.
Loveday.

4.

To enrich; to exalt; to benefit.

They stuck not to say that the king cared not to plume his nobility and people to feather himself.
Bacon.

Dryden.

5.

To tread, as a cock.

Dryden.

To feather one's nest, to provide for one's self especially from property belonging to another, confided to one's care; -- an expression taken from the practice of birds which collect feathers for the lining of their nests. -- To feather an oar Naut, to turn it when it leaves the water so that the blade will be horizontal and offer the least resistance to air while reaching for another stroke. -- To tar and feather a person, to smear him with tar and cover him with feathers, as a punishment or an indignity.